1. Technical Field
The present invention relates generally to client-server computing over the Internet and more particularly to a method for ensuring that a Web browser obtains high availability to Web services.
3. Description of the Related Art
The World Wide Web is the Internet's multimedia information retrieval system. In the Web environment, client machines effect transactions to Web servers using the Hypertext Transfer Protocol (HTTP), which is a known application protocol providing users access to files (e.g., text, graphics, images, sound, video, etc.) using a standard page description language known as Hypertext Markup Language (HTML). HTML provides basic document formatting and allows the developer to specify "links" to other servers and files. In the Internet paradigm, a network path to a server is identified by a so-called Uniform Resource Locator (URL) having a special syntax for defining a network connection. Use of an HTML-compatible browser (e.g., Netscape Navigator or Microsoft Internet Explorer) at a client machine involves specification of a link via the URL.
When the user of the browser specifies a link, the client issues a request to a naming service to map a hostname (in the URL) to a particular network IP address at which the server is located. The naming service returns a list of one or more IP addresses that can respond to the request. Using one of the IP addresses, the browser establishes a connection to a server. If the server is available, it returns a document or other object formatted according to HTML. If the server is not available or overloaded, however, the user may receive an error message, e.g., "Server not responding" or the like. This is undesirable.
As Web browsers become the primary interface for access to many network and server services, the problem arises of how best to ensure "availability" of Web services in a manner that is also both scaleable and balanced. Users of client machines desire prompt and efficient access to Web servers so that Web pages download seamlessly and as fast as practicable given the physical constraints of the applicable network connections. Web site providers desire to operate an appropriate number of servers to handle client loads in a scaleable and balanced manner. An efficient network ensures that clients can find an available server, even if servers in the network fail.
A number of server-based solutions have been proposed and/or implemented to attempt to ensure that Internet services remain available, scaleable and well-balanced. One type of approach is the "front end" server configuration or cluster, wherein a plurality of "proxy" servers are maintained at a particular access location common to multiple clients, with the servers being used to mirror high traffic Web sites. While the front end approach provides certain improved service, it is not readily scaleable. Another approach utilizes a "round robin" nameserver to hand out one of a list of IP addresses each time the nameserver receives an HTTP request. This approach does a poor job of balancing request load, and its effectiveness is limited due to client caching.
It would be highly desirable to provide a client-side solution to ensure "availability" of Web services to a Web browser.